Implementing QoS Aware Component-Based Applications

By QoS (Quality of Service), we often refer to a set of quality requirements on the collective behavior of one or more objects. These requirements enable the provision of better service to certain data flows. The developer can either increase the priority of a data flow or limit the priority of another data flow, in order to tune the proper “parameters” that support quality requirements. Nowadays, the use of contracts for software components is a novel way of guaranteeing their quality. It is a rather cumbersome task to design components that comply with contracts, because different problem dimensions or quality aspects have to be addressed at the same time. In this paper, we employ a simple methodology to show how we can design and develop QoS components that are based on Aspect-Oriented Programming and Model Transformation. We use a Tele-Medicine framework to show how we can embed to the final product a set of QoS contracts. We implement two such contracts that support QoS in communication and teleconferencing. We describe all the steps of the analysis, design and implementation in order to denote the advantages of using this novel way of weaving quality contracts into QoS applications.